Studio integrato di rocce sedimentarie da cave siciliane di interesse storico-artistico

Indagini EPR su legni moderni e antichi

La tecnica EPR e'stata applicata allo studio di legni moderni ed antichi. I legni deteriorati mostrano un segnale EPR molto piu'intenso di quelli non deteriorati. Questo risultato puo' essere spiegato dall'aumento dei radicali liberi nei campioni deteriorati.

Rilassometria 1H-NMR per la caratterizzazione di legni integri e degradati

La caratterizzazione del legno riveste un particolare ruolo negli studi volti alla conservazione di manufatti lignei di interesse storico-artistico-archeologico. Le proprietà meccaniche del legno dipendono dalla specie, dal contenuto d’acqua, dalla direzione delle fibre, dalla porosità, dalla distribuzione dei pori e, in generale, da un insieme di condizioni che non sempre sono facilmente misurabili e controllabili. Di particolare interesse sono i metodi di indagine non invasivi e non distruttivi; tra questi si sta affermando la Risonanza Magnetica Nucleare (NMR) [1,2]. In questo lavoro metodi di Rilassometria 1H-NMR, messi a punto per il tessuto osseo [3], sono stati applicati allo studio …

In-situ NMR diagnostics on building materials of the greek-roman theatre of Taormina.

Rilassometria NMR in legni moderni e in legni trattati e non trattati provenienti da una statua lignea del XVI secolo

From laboratory to in-situ Nuclear magnetic Resonance Diagnostics: an application to building materials of the Greek-Roman Theater of Taormina

Analisi critica delle curve di rilassamento in materiali lapidei provenienti da beni culturali.

Validity of NMR pore-size analysis of cultutal heritage ancient building materials containing magnetic impurities

NMR relaxation time distributions, obtained with laboratory and portable devices, are utilized to characterize the pore-size distributions of building materials coming from the Roman remains of the Greek-Roman Theatre of Taormina. To validate the interpretation of relaxation data in terms of pore-size distribution, comparison of results from standard and in situ NMR experiments with results of the mercury intrusion porosimetry (MIP) has been made. Although the pore-size distributions can be obtained by NMR in terms of either longitudinal (T-1) or transverse (T-2) relaxation times distributions, the shorter duration of the T-2 measurement makes it, in principle, preferable, although the dete…

EPR surveys on modern and ancient woods.

Applicazione di trasformate wavelet per la riduzione del rumore nelle immagini NMR di rocce sedimentarie

Il sempre crescente interesse verso i Beni Culturali suscita molteplici problematiche inerenti la salvaguardia e la diagnosi del loro stato di conservazione. In questo ambito, lo studio delle caratteristiche, quali ad esempio le proprietà capillari delle rocce sedimentarie, ricopre un’importanza cruciale non solo per studiare lo stato di conservazione ma anche per fornire utili indicazioni sulle possibili tecniche e sui materiali da utilizzare negli eventuali trattamenti di protezione e restauro. Al fine di ottenere approfondite informazioni sulle proprietà capillari, il presente lavoro propone un metodo matematico utile nello studio della cinetica di assorbimento capillare. Lo studio è sta…

Solid-liquid nuclear magnetic resonance relaxation and signal amplitude relationships with ranking of seasoned softwoods and hardwoods

In 1H NMR (Nuclear Magnetic Resonance) relaxation measurements for a set of eight hardwood and softwood samples, each Free Induction Decay (FID) is fit by the sum of a “Solid” signal of the form A exp[−c(t/Ts)2] [1−g(t/Ts)2+h(t/Ts)4] plus a “Liquid” signal B exp(−t/T2 FID). Distributions of longitudinal (T1) relaxation times were computed separately for the Solid and Liquid components, giving also the Solid/Liquid 1H ratio α. From measurements on the samples dried, seasoned, and hydrated, the moisture content, (Liquid/Solid weight ratio) was found to be approximately 0.50/α. For each of the “Seasoned” samples (10-13% moisture content) a single T1 peak was found for the Solid and two for the…

NMR relaxation in modern wood and treated and untreated wood from a XVI century wooden statue

Longitudinal (T1) relaxation data are presented for European lime (Tilia cordata Mill) wood samples, a modern sample and two from a XVI century wooden statue, one of which samples is treated with Paraloid B72 for preservation. The 1H signals from liquid and solid are separated in the free induction decays (FID). T1 distributions are obtained by UPEN and show two resolved peaks for the liquid component of either untreated wood but a wide distribution for the liquid of the treated sample. In each case, the solid component showed a single peak, which for either untreated sample was at about the position of the longer T1 liquid peak. We compute geometric-mean times, T1-gm, 2.1 and 36 ms for the…

Misure di rilassamento 1H-NMR per la classificazione di essenze lignee e per lo studio di trattamenti protettivi e consolidanti

Nuclear Magnetic Resonance for Cultural Heritage

Abstract Nuclear magnetic resonance (NMR) portable devices are now being used for nondestructive in situ analysis of water content, pore space structure and protective treatment performance in porous media in the field of cultural heritage. It is a standard procedure to invert T 1 and T 2 relaxation data of fully water-saturated samples to get “pore size” distributions, but the use of T 2 requires great caution. It is well known that dephasing effects due to water molecule diffusion in a magnetic field gradient can affect transverse relaxation data, even if the smallest experimentally available half echo time τ is used in Carr–Purcell–Meiboom–Gill experiments. When a portable single-sided N…

Indagini EPR su legni moderni e antichi.

Rilassometria NMR applicata allo studio della statua lignea di San Nicola di Mira (XVI secolo) al museo Diocesano di Palermo

In un recente studio condotto mediante Rilassometria NMR del nucleo 1H su legni moderni stagionati è stato mostrato che è possibile separare la curva di rilassamento della componente longitudinale della magnetizzazione nucleare dei nuclei 1H meno mobili (componente “solida”), attribuibili alle macromolecole, da quella dei nuclei a maggior mobilità (componente “liquida”), attribuibili all’acqua. Oltre a permettere di verificare la proporzionalità diretta tra ampiezza della componente liquida del segnale e massa d’acqua, l’analisi delle curve di rilassamento mediante distribuzioni quasi-continue del tempo di rilassamento longitudinale T1 permette di classificare le essenze lignee esaminate, m…

Integrated techniques to evaluate the features of sedimentary rocks of archaeological areas of sicily.

Sicily includes a great variety of lithologies, giving a high complexity to the geologic landscape. Their prevalent lithology is sedimentary. It is well known that rocks of sedimentary origin, compared with metamorphic and volcanic deposits, can be relatively soft and hence fairly easy to model. Nevertheless, this workability advantage is a drawback for Cultural Heritage applications. In fact, these materials show a high porosity, with pore-size distributions that lead to deterioration through absorption of water. In this paper, several sedimentary rocks used in historical Cultural Heritage items of Sicily, from "Magna Graecia" to nowadays, are classified for mineralogical features, chemica…

Confronto TAC – MRI per lo studio della cinetica di assorbimento dell’acqua in materiali lapidei

Vengono messe a confronto due tecniche, la Risonanza Magnetica (MRI) e la tomografia assiale computerizzata (TAC), per ottenere informazioni quantitative sulla cinetica di assorbimento dell’acqua in sezioni interne di materiali lapidei. Entrambe le tecniche permettono di studiare adeguatamente il fenomeno. Nel caso in cui si formi un fronte di bagnamento, come per la Pietra di Lecce, l’analisi delle immagini consente di determinare in modo quantitativo l’altezza di risalita in funzione del tempo ed i dati possono essere interpretati alla luce del modello di Washburn per l’assorbimento capillare. Nel caso in cui il fronte non si formi, come per campioni di biocalcareite provenienti da una ca…

Water capillary absorption in porous media in different wettability conditions studied by Quantitative MRI and X-ray CT

X-ray computed tomography (CT) and magnetic resonance imaging (MRI) have been successfully applied to study both the capillary properties of several samples of Lecce stone and the performances of treatments used for protection and conservation of historical stone artifacts. The presence of water inside the sample may be visualized by both MRI and X-ray CT. For the treated samples, the different dynamics of water absorption gives indirectly the efficacy of the polymer in the rock.

Preliminary 1H NMR study on archaeological waterlogged wood.

Magnetic Resonance Relaxation (MRR) and Magnetic Resonance Imaging (MRI) are powerful tools to obtain detailed information on the pore space structure that one is unlikely to obtain in other ways. These techniques are particularly suitable for Cultural Heritage materials, because they use water 1H nuclei as a probe. Interaction with water is one of the main causes of deterioration of materials. Porous structure in wood, for example, favours the penetration of water, which can carry polluting substances and promote mould growth. A particular case is waterlogged wood from underwater discoveries and moist sites; in fact, these finds are very fragile because of chemical, physical and biological…

Noise reduction in magnetic resonance images by Wavelet transforms: an application to the study of capillary water absorption in sedimentary rocks

Magnetic resonance imaging (MRI) is a powerful technique to study capillary water absorption kinetics in sedimentary rocks. However, the noise in the images can limit the correct identification and the quantitative measurement of the average height reached by the wetting front inside the porous material where imbibition occurs. Therefore, denoising methods can be applied to improve the image quality for a more accurate analysis, without the disadvantages of longer acquisition times. This study attempts to improve the signal-to-noise ratio of the images acquired by MRI on a sedimentary rock (Pietra di Lecce) using a waveletbased thresholding technique. The idea is to average some slightly di…